1. Field of the Invention
The present invention relates to a semiconductor device.
2. Related Art
Heretofore, a semiconductor device having power semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors) has been known. The semiconductor device having power semiconductor elements, in general, has a structure wherein an insulating substrate on which semiconductor elements are mounted is mounted on a heat dissipation metal base plate, and the insulating substrate is covered with a surrounding case attached to the peripheral edge of the metal base plate.
As a heretofore known technology of this kind of semiconductor device, a structure wherein pairs of positive and negative direct current input terminals are arrayed in sidewalls, which form two opposing sides of a surrounding case having a substantially rectangular shape in plan view, so that the input terminals of the same pole are opposed to each other with an insulating substrate sandwiched therebetween, is disclosed (see, for example, Japanese Patent Application Publication No. JP-A-7-111310).
Also, as another heretofore known technology, a structure wherein two plate-like terminal conductors through which currents flow in opposite directions are disposed in a surrounding case in a condition in which the plate surfaces of the terminal conductors are parallel to and close to each other, thereby cancelling out the inductance of wires generated by a current flowing from the respective electrodes of semiconductor elements to external connection terminals, is disclosed (see, for example, Japanese Patent Application Publication No. JP-B-7-83087).
Currently, a surrounding case used in the heretofore known semiconductor devices, employing the heretofore known technologies, adopts a structure wherein two external connection terminals of the same polarity are disposed in each of sidewalls forming two opposing sides, of four peripheral sides of the surrounding case, and two terminal conductors opposed to and spaced a fixed distance from each other are provided inside the surrounding case. Connection terminals for connecting with a circuit-patterned conductive foil on the insulating substrate are formed on the respective terminal conductors. A ceramic substrate wherein a circuit-patterned conductive foil of copper (Cu) is affixed to each surface of an insulating layer made of alumina (Al2O3), aluminum nitride (AlN), or the like which is an insulating material is commonly used for the insulating substrate.
When manufacturing a semiconductor device using the heretofore described surrounding case, firstly, an insulating substrate on which semiconductor elements are mounted is mounted on and fixed to a metal base plate. Next, after the metal base plate has been covered with the surrounding case and positioned in place, the peripheral edge of the metal base plate and the surrounding base are attached by an adhesive, thereby mounting the surrounding case on the metal base plate. Further, connection terminals of terminal conductors provided in the surrounding case and a conductive foil on the insulating substrate are soldered using paste solder.
Next, a description will be given of a structure of a heretofore known semiconductor device including the surrounding case. FIGS. 7A and 7B are an illustration showing a structure of the heretofore known semiconductor device. FIG. 7A is a structure in plan view, and FIG. 7B is a structure in section view. As shown in FIGS. 7A and 7B, the heretofore known semiconductor device 100 includes a heat dissipation metal base plate 40, an insulating substrate 41, and a surrounding case 50. The insulating substrate 41 is mounted on the metal base plate 40, and the surrounding case 50 is attached to the peripheral edge of the metal base plate 40. Semiconductor elements omitted from the drawing are mounted on the insulating substrate 41.
The surrounding case 50, being a case molded from a resin, includes metal external connection terminals 63-1, 63-2, 63-3, and 63-4, and terminal conductors 60-1 and 60-2, which are integrated by insert molding. The external connection terminals 63-1, 63-2, 63-3, and 63-4 and terminal conductors 60-1 and 60-2 are molded by processing a metal plate such as a copper plate. The external connection terminals 63-1 and 63-2 and terminal conductor 60-1 are electrically connected together, and the external connection terminals 63-3 and 63-4 and terminal conductor 60-2 are electrically connected together.
The external connection terminals 63-1 and 63-2 of one polarity, which are opposed to each other with the terminal conductor 60-1 sandwiched therebetween, and the external connection terminals 63-3 and 63-4 of the other polarity, which are opposed to each other with the terminal conductor 60-2 sandwiched therebetween, are provided in sidewalls 50a and 50b forming two opposing sides, of four peripheral sides of the surrounding case 50 having a substantially rectangular shape in plan view. The terminal conductors 60-1 and 60-2 are molded integrally with the surrounding case 50, and a total of four portions at two pairs of end portions of the terminal conductors 60-1 and 60-2 are fixed in the sidewalls 50a and 50b of the surrounding case 50 using a resin. Normally, the terminal conductors 60-1 and 60-2 are disposed in the surrounding case 50 so that the plate surfaces of the terminal conductors 60-1 and 60-2 are parallel to the front surface of the insulating substrate 41 when the surrounding case 50 is placed on the metal base plate 40 in a room temperature condition.
The terminal conductor 60-1 is disposed above the insulating substrate 41 and below the terminal conductor 60-2. The shape in plan view of the terminal conductor 60-1 is substantially linear. The shape in plan view of the terminal conductor 60-2 is a shape bent so as to form the contour of a trapezoid with the lower base removed (hereafter, a trapezoidal frame shape). Also, internal wiring connection terminals 61-1 and 61-2 are provided on the terminal conductors 60-1 and 60-2 respectively. The connection terminals 61-1 and 61-2 are formed on the terminal conductors 60-1 and 60-2 in such a condition as to protrude downward in the direction, in which the insulating substrate 41 is positioned, from the respective heights at which the terminal conductors 60-1 and 60-2 are positioned (hereafter, a description will be given with the insulating substrate 41 side as the lower side and the terminal conductor 60-2 side as the upper side).
The connection terminals 61-1 and 61-2 and a conductive foil (not shown) on the insulating substrate 41 are soldered using paste solder. By soldering the connection terminals 61-1 and 61-2 and the conductive foil on the insulating substrate 41, the external connection terminals 63-1, 63-2, 63-3, and 63-4 protruding externally from the surrounding case 50 establish electrical continuity with the insulating substrate 41 on which a circuit pattern or a conductive material is laid. By so doing, the insulating substrate 41, on which are mounted the semiconductor elements inside the semiconductor device 100, and another external system can be electrically connected via the external connection terminals 63-1, 63-2, 63-3, and 63-4.